Field of the Invention
Embodiments of the invention relate to a multi-view autostereoscopic display and a method for controlling an optimal viewing distance thereof.
Discussion of the Related Art
As stereoscopic image reproduction technology is applied to display devices such as a television and a monitor, people can easily view three-dimensional (3D) stereoscopic images even at home. A 3D display may be classified into a stereoscopic display using glasses and an autostereoscopic display called a glasses-free 3D display. The stereoscopic display separates a left eye image and a right eye image using polarization glasses or liquid crystal shutter glasses, thereby implementing a stereoscopic image. Further, the autostereoscopic display installs an optical element, such as a parallax barrier or a lenticular lens (hereinafter abbreviated to “lens”), in front of or behind a display screen and separates optical axes of a left eye image and a right eye image, thereby implementing a stereoscopic image.
As shown in FIG. 1, the autostereoscopic display calculates an optimal viewing distance OVD, at which a viewer can properly view a stereoscopic image, based on a back length between a pixel array PIX of a display panel and a lens LENS, a focal length of the lens LENS, a pixel pitch Ppix, a lens pitch Plens, a distance between a left eye and a right eye of the viewer, etc. In FIG. 1, the back length, the focal length of the lens LENS, the pixel pitch Ppix, the lens pitch Plens, and the distance between the left and right eyes of the viewer are fixed to constant values. Further, the distance between the left and right eyes of the viewer is about 65 mm for average adults.
Thus, as shown in FIG. 1, the optimal viewing distance OVD of the autostereoscopic display is fixed to a specific position. When the adjustment of the optimal viewing distance OVD is required, the back length or the focal length of the lens LENS has to be changed. Even when the autostereoscopic display has a barrier instead of the lens LENS shown in FIG. 1, the optimal viewing distance OVD is fixed to a specific position.
In FIG. 1, “REZ” denotes a right eye viewing zone where pixels R (hereinafter, referred to as “right eye pixels”), to which a right eye image is formed, can be seen, and “LEZ” denotes a left eye viewing zone where pixels L (hereinafter, referred to as “left eye pixels”), to which a left eye image is formed, can be seen. “PSUBS” is a transparent substrate for securing the back length between the pixel array PIX and the lens LENS.
If the viewer moves forward or backward from the optimal viewing distance OVD, the viewer may see both the left eye pixels and the right eye pixels through his or her eye (right eye or left eye) and thus may experience 3D crosstalk. In addition, the autostereoscopic display can be implemented as a multi-view system. In the multi-view system, a multi-view image is formed to the pixel array PIX, thereby enabling the viewer to see a stereoscopic image at different positions from the optimal viewing distance OVD. In the multi-view system, if the viewer moves forward or backward from the optimal viewing distance OVD, view images seen through one eye of the viewer are overlapped, thus making the viewer feel the 3D crosstalk. Thus, only when the viewer sees the image at the optimal viewing distance OVD of the autostereoscopic display, the viewer may see the normal stereoscopic image.
One method for controlling the optimal viewing distance of the autostereoscopic display has been proposed to estimate a view image of the pixel array the viewer sees when the viewer moves out of the optimal viewing distance, and modify pixel data of the view image the viewer sees. In this method, examples of modifying the pixel data include a shifting method and a scaling method. The shifting method moves a view map from side to side when the viewer moves from side to side along an x-axis. The scaling method adjusts a ratio of the view map when the viewer goes close to or far from the display panel along a z-axis.
In addition, the x-axis is parallel to the screen of the display panel, and the z-axis is vertical to the screen of the display panel. However, the related art method for controlling the optimal viewing distance is done by applying the same algorithm to the display panel. Further, because the related art method for controlling the optimal viewing distance did not consider a refractive index of a lens of an optical element, the method is not accurate. A related art method for controlling the optimal viewing distance is disclosed in U.S. publication No. 2009/0123030 A1 (2009 May 14).